Climate change. For some reason, certain people just don’t believe it’s real. Even Scott Pruitt, the man President Trump named to head the Environmental Protection Agency, isn’t steadfast about global warming and what causes it. But years of scientific study have shown the planet is getting warmer. What gives? According to Bill Nye, the answer is simple: cognitive dissonance.

“People have a certain worldview; [then] they’re confronted with evidence that conflicts with the worldview, so they have dissonance, conflict in their minds,” Nye says. “[So] instead of changing your worldview, which you may have held your entire life, you dismiss the evidence—and along with that you dismiss the authorities that may have provided the evidence.”

An understanding of climate change denial is just one of the many answers the Science Guy provides in the video above, in which the star of Netflix’s new series Bill Nye Saves the World takes questions from Twitter and provides clear explanations for some of science’s thornier questions. Press play to learn more about evolution, dark matter, avocados, and that most important of questions: Magnets, how do they work? Short answer: “Magic!” (Just kidding.)